Cyanobacteria are small, prokaryotic, generally aquatic organisms. Some cyanobacterial species can be genetically engineered in order to produce compounds of interest by utilizing light and carbon dioxide. These compounds of interest can include biofuels, industrial chemicals, pharmaceuticals, nutrients, carotenoids, food supplements and other compounds such as lipids. Owing to the fact that cyanobacteria are capable of fixing carbon dioxide as a carbon source for photoautotrophic growth, they do not require the input of organic carbon as feedstock and generally only need few nutrients. Some cyanobacterial species such as Synechococcus or Synechocystis have been genetically engineered in order to produce various compounds of interest such as ethanol (see for example U.S. Pat. No. 6,699,696 and U.S. Pat. No. 6,306,639, as well as PCT patent application WO 2009/098089 A2). Cyanobacterial cells can grow under a large variety of different growth conditions including sweet water as well as brackish water and can also thrive at very different temperatures.
The cyanobacterial genus Chlorogloeopsis belongs to the subsection V of cyanobacteria and is a heterocyst forming nitrogen fixing cyanobacterial genus, which can among others be isolated from hot springs (original publications: Mitra, A. A. and Pandey, D. C. (1967) “On a new genus of the blue-green alga Chlorogloeopsis with remarks on the production of heterocysts in the alga”; Phykos 5: pages 106 to 114 and Mitra, A. K. (1950): Two new algae from Indian soils. Ann. Bot. London. N. S. 14: 457-464).
The scientific publication Stucken et al.: “Transformation and Conjugal Transfer of Foreign Genes into the Filamentous Multicellular Cyanobacteria (Subsection V) Fischerella and Chlorogloeopsis”; Curr Microbiol., 2012 November; 65(5):552-560, describes successful transformation of Cyanobacteria of subsection V by introducing the gene coding for the green fluorescent protein GFP into Fischerella and Chlorogloeopsis so that these cells were able to express the GFP reporter protein under two different promoters: the nitrogen regulated PglnA and the strong constitutive E. coli promoter Ptrc. For both strains partial removal of the exopolysaccharide sheath by salt washing was a critical step. However, the expression of the green fluorescent protein, which is not an enzyme, does not greatly affect the metabolism of the cyanobacterial cells because it does not consume metabolically important intermediates. This is in contrast to enzymes which are expressed to catalyze the production of chemical compounds of interest. Therefore this publication does not disclose any information on how a stable production of chemical compounds such as ethanol in Chlorogloeopsis can be achieved.
What is needed in the art is a new cyanobacterial strain for the production of ethanol, which can withstand hard culturing conditions and the metabolic stress associated with the production of chemical compounds of interest.